Are fast radio bursts a source of gravitational waves?

We know that we entered the era of gravitational astronomy in 2015, almost 100 years after Albert Einstein finally formed his relativistic theory of gravity, the famous general theory of relativity. She describesspace-time as an elastic and therefore deformable medium, capable of oscillating and oscillating like the surface of water and even turning into an equivalent to it foam in a mode with a predominance of quantum effects.

That gravitational waves can be issued by all distributions to matter which are described as physics called quadrupoles in their jargon, which is not true for all sources. In this way, star which would explode in a perfectly spherical manner, would not produce gravitational waves. On the other hand, this is indeed a case of a couplestars in orbit around each other like the earth and moon. I’episode however, only strong with compact stars such as black holes as well as neutron starsand especially when they are about to collide and merge.

As well as light stars give us valuable information about phenomena and objects in astrophysics, “gravitational light” so to speak is rich in information, even more so if we can combine these two types of messages, and it is also in such a way that it has been shown that some gamma- the bursts were indeed what we thought were neutron star collisions, producing what is called kilonovae.

Video presentation of Virgo and the hunt for gravitational waves. © CNRS

From kilonova to FRB

Encouraged by these results, the collaborators Ligo as well as Virgonow famous gravitational wave detectors, decided to try to shed light on the nature of the still mysterious fast radio bursts (fast radio burstsor FRB, in English) trying to detect gravitational waves that could be associated with them, as they explain in an open access article on arXiv.

FRBs, also called “Lorimer Bursts” after their discoverer, are transient signals equivalent to allenergy radiated Sun in the visible range during the year seems to be released in a maximum of a few milliseconds in the radio region. Initially, it was believed that they could be associated with explosions. supernovae and collisions of compact stars, such as a neutron star with a black hole, but the detection of repeated FRBs for the same source in the firmament (however, this does not apply to all FRBs) demonstrated that this cannot be the case. We know yet today that they are located in the billionslight years belonging Milky Way and there are indications that they may be related to magnetarsthese neutron stars magnetic fields especially intense.

Since 2018, with the opening of a new radio telescope scale at the Dominion Radio Astrophysical Observatory in British Columbia, Canada, astrophysicists had an instrument particularly suited to detecting FRBs, and quickly found hundreds of them. Canadian intensity mapping experiment.hydrogen “, or, in English, Canadian Hydrogen Intensity Mapping Experimentshort for Chime.

Presentation video of the radio telescope Chime. For a fairly accurate French translation, click on the white box in the lower right corner. Then there are English subtitles. Then click on the gear to the right of the rectangle, then on “Subtitles” and finally on “Translate automatically”. Select “French”. © McGill University

At present, we know quite well how to localize FRBs in the firmament and, by studying their effect on spectra radio interactions of the emitted signal with electrons freely in observable space, we can determine the distance to the Milky Way. The longer the transit time, the greater the difference between the arrival time of radio pulses in the high and low parts of the spectrum of these pulses.

The combination of the Ligo and Virgo detectors also makes it possible to locate the source of gravitational waves in the firmament and therefore to do multi-messenger astronomy, as we say in this case, to see if the electromagnetic signal is related to the gravitational signal. with two sources coinciding in the vault of heaven.

Thus, about 350 FRBs provided data that can be linked to Ligo and Virgo. Therefore, the researchers studied the data recorded by these two instruments during the discovery campaign, which took place between April and September 2019.

As explained in the press release from the Ligo and Virgo collaborations, two different detection methods were implemented. The first focuses on finding matches only between two sources, while the second is based on the fact that we know a priori general view of the spectrum of waves emitted by collisions of compact stars. Thus, the first method does not depend on some assumptions about the nature of FRBs, while the second does not, and it only applies to non-repeating FRBs.

The first method examined 39 FRBs, the second – 22. The results are currently negative, but this does not mean that they will remain so, because the gravitational signal may not be detected for nearby FRBs. The sensitivity of the detectors of these waves increases over time, we can get good surprises, and it is for this reason that studies of this type will continue, already in the data that will be collected in the next six months with Ligo and Virgo. .

Interested in what you just read?

Leave a Comment